Support is requested for a Keystone Symposia meeting entitled Systems Immunology: From Molecular Networks to Human Biology, organized by Ronald N. Germain, Aviv Regev, Nir Hacohen and Dana Pe'er. The meeting will be held in Big Sky, Montana from January 10-15, 2016. This meeting will constitute a unique opportunity for the lymphocyte activation field to transition from reductionist studies to a more integrated approach for analyzing immune physiology and pathology from the molecular (signal transduction) to the medical (human clinical studies) scales. It will highlight the latest advances in large-scale, quantitative data collection and computational analysis as applied to biochemical aspects of immune cell activation and function, multicellular behavior in tissues and model organisms, and human immune function in health and disease. Emphasis will be placed on understanding how biological function emerges from the interaction of multiple components in networks and pathways, on the construction of quantitative models that permit predictions about systems behavior that can be tested experimentally, and on identification of reliable biomarkers and insight into disease pathogenesis that can be acquired from deep analysis of large-scale, multi-parameter data collection in humans. The speakers hail from various areas in systems immunology, ranging from those modeling discrete biochemical pathways and cell activation processes, to those developing new tools for measurement of such molecular events, to imagers studying immune cells in situ, to those doing omic-scale studies on humans in response to vaccines or in patients suffering from autoimmune or immunodeficiency syndromes. We anticipate that this meeting will attract participants across the range of immunological disciplines, from the most basic to the clinical, and be of interest to systems biologists in general.